1. Field of the Invention
The invention relates to extraction apparatuses for preparing beverages or the like from an extraction material, for example ground coffee, which is contained in a capsule. Said invention relates, in particular, to a discharge device for discharging an extraction product from the capsule, to a puncturing device for puncturing the portion pack, and to an extraction apparatus having a discharge device and/or puncturing device of this kind.
2. Description of Related Art
Extraction apparatuses for preparing beverages or the like from an extraction material which is contained in a portion pack are known, for example, as coffee or espresso machines and continue to enjoy increasing popularity. In many corresponding systems, the portion packs are in the form of capsules in which the extraction material is enclosed, for example, in an air-tight manner. For the purpose of extraction, the capsule is punctured from two opposite sides. An extraction liquid—generally hot water—is introduced on the first side. The extraction product is discharged from the capsule on the second side. Depending on the beverage to be prepared and the system, a considerable pressure, of for example 5-20 bar, may prevail in the interior of the capsule in the process, this making great demands on the puncturing and discharge mechanism.
The capsule systems in which water is introduced into the capsule on an injection side, while the capsule is initially intact on the extraction side, have been disclosed as corresponding systems in the first instance. Under the pressure of the introduced water, the extraction-side boundary of the capsule is pressed against a, for example ribbed, structure and, in the process, subjected to such stress that it breaks and the extraction product can flow out of the capsule. A system of this kind can operate only with a material which is only very slightly plastically expandable and has a limited stress load capacity which is reached when the material is pressed against a rib or the like by the internal pressure in the capsule. To date, it has only been possible to use aluminum as a material of this kind. Examples of systems of this kind are disclosed in EP 0 521 188 and U.S. Pat. No. 5,897,899.
Further disclosed have been systems in which the capsule is pierced by a perforation tip on the extraction side, for example by positioning in the brewing chamber and before the brewing process is started. In systems of this kind, the extraction product is passed through the perforation spike; the coffee grounds remain in the capsule. The capsule wall of systems of this kind can be composed of plastic—for example polypropylene with an oxygen-tight barrier layer—, with the perforation tips then having to be very sharp in this case on account of the very high elongation at break of such materials; puncturing of plastic capsules of this kind is not trivial.
WO 2008/023057 describes a corresponding means for penetrating a portion pack using perforation tips which each have a surface which is inclined in the perforation direction and has openings in a perforated sieve structure. The purpose of these means is to improve conduction properties. However, the highly complex production method is a disadvantage.
EP 1 783 066 and WO 95/25457 each describe a discharge device having a large number of perforation tips, with each perforation tip having a passage opening or a passage channel. Even though the discharge device in these documents is called a “filter plate”, the passage openings are provided in the respective perforation tips and not in a plate-like element which is arranged outside the capsule. The passage openings in discharge devices of this kind necessarily have a certain minimum diameter of, for example, approximately 400 μm, so that enough liquid can pass through in a sufficiently reliable manner and without blockages. However, at this size, the opening has only a limited filter effect, and therefore fine particles of the coffee grounds (or residues of another extraction material) can reach the beverage—besides, the extraction material meets very high requirements in respect of the regularity of particle size, this entailing additional expenditure. It is an object of the invention to provide a discharge device and a puncturing device for extraction apparatuses and also a corresponding extraction apparatus, which devices and apparatus overcome the disadvantages of the prior art and have good conduction properties and are simple to produce.